Thanks to the tip from Commodore47 mentioning returning to inside of the stop block.
I used "my favorite piece of yellow pine" to slightly lift the slide about 1" and pivot-push
the slide slightly back onto the top of the stop block. The attached pic shows the
positioning of the board, although you need to envision the shell up and slide forward,
but just in front of the stop block. I then pushed back on the front corner of the slide,
and it dropped back to the in-range max forward position.
My lesson learned is to pull the slide out with moderate effort, although the effort needed may vary at times.
Happy Camping!